Method and apparatus for calibration and quality assurance of nuclear medicine imaging

ABSTRACT

A method for calibration and/or quality assurance of nuclear medicine imaging, in which functional information of the organs to be studied is achieved by inserting radioactive solution emitting detectable radiation in the organs of a phantom simulating the organs to be studied and by detecting the radiation. The filling and emptying of the organs of the phantom to be studied is simulated by regulation of the detectable radiation from the phantom. The organs to be simulated by the phantom are in form of containers filled with radioactive solution, the apparatus further comprising movable isolating parts, like steel plates, between the containers and the gamma camera to isolate radiation from the containers to the camera. The invention is also concerned with an arrangement comprising the apparatus of the invention and a gamma camera.

TECHNICAL FIELD

The invention is concerned with a method and apparatus for calibrationand quality assurance of nuclear medicine imaging as e.g. radionucliderenography by means of a phantom. The invention is also concerned withan arrangement comprising the apparatus of the invention.

BACKGROUND ART

The quality of nuclear medicine imaging, as in all imaging modalities,depends on the whole investigation procedure. If any of the steps isunsatisfactory, the result is not reliable. Most of the individual stepsand the facility can, and should, be checked by employees of departmentsregularly, but this is not enough. The need for overall qualityassurance by independent outside observers is taking place in medicalimaging.

The basic principle of diagnostic nuclear medicine is the use ofpharmaceuticals capable of carrying radionuclides that emit penetratingradiation. First the radionuclide and the pharmaceutical are combined,then the compound is injected into the circulatory system of thepatient. The distribution of the radiopharmaceutical within the body canthen be detected using a gamma camera to image and quantify regionalphysiological biochemical processes. For example dynamic radionucliderenal imaging (renography) gives functional and structural informationabout the kidneys and the urinary tract non-invasively.

The best way to compare the quality of imaging between laboratories is amulticentre study with a human being afflicted with known diseases. Dueto ethical aspects and radiation safety it is, however, not possible. Ananalogue approach is to use organ-like phantoms. Zubovskii et al.(Zubovskii G A. Devishev M I, Ivanov E V, Andreeva O V and Luchkov A B1983 Radionuclide studies with a dynamic kidney phantom Med. Radiol.(Mosk) 28 77-82 (in Russian)) have developed a renography phantom basedon the flow itself of the radioactive liquid. No quantitative comparisonwith patient studies or repeatability of the phantom simulations exist.Neither is there presented any solutions for controlling of the flow ofthe radioactive solution inside the simulated organs to ensurerepeatability.

Other kinds of dynamic phantoms exist. Sulab Oy in Helsinki, Finland ismarketing a dynamic cardiac phantom (model DCP-101), wherein the cardiacfunction of the heart is simulated by moving lead shields. The degree ofshielding of the radioactive ventricle area determines the ejectionfraction. CAPINTEC, INC. sells a cardiac phantom (CP-201 Vanderbiltcardiac phantom), in which rotating ellipsoids simulate dynamic leftatrium and verticle motion at variable heart rates. A variety of patientconditions can be simulated by varying the concentration of theradioactive solution in the ellipsoids and by adjusting the rate ofrotation (variable pulse rate) and attenuator thickness. Staticbackground represents the right heart chambers, aorta and generalbackground tissues.

There are commercially available phantoms also for example for studyingof brain perfusion single photon emission tomography (SPET) and bonesbut no commercially available renography phantoms for external qualityassurance purposes.

An object of this invention is therefore the developing of a newphantom, with which it is possible to simulate different patientsituations and organs.

Another object of this invention is the developing of a phantom, withwhich the flows and mixing of the radiopharmaceutical can be controlledand repeatability is possible.

SUMMARY OF THE INVENTION

To achieve the objects of the invention, there is has been developed amethod for calibration and/or quality assurance of nuclear medicineimaging, in which functional information of the organs to be studied isachieved by inserting radioactive solution emitting detectable radiationin the organs of a phantom simulating the organs to be studied, and bydetecting the radiation, which is mainly characterized in that thefilling and emptying of the organs of the phantom to be studied issimulated by regulation of the detectable radiation from the phantom bysuccessively removing respective adding isolating parts between thephantom and the detector of the radiation.

The arrangement of the invention mainly comprises a phantom simulatingthe organs to be studied and a gamma camera for detecting of theradiation and imaging of the organs. The organs to be simulated by thephantom are in form of containers filled with radioactive solution, andthe phantom further comprises movable isolating parts between thecontainers and the gamma camera to isolate radiation from the containersto the camera.

In the preferred embodiments, the regulation of the detectable radiationis carried out in accordance with an exact time schedule to simulate agiven patient situation. For example regional time activity curves overthe kidneys and the heart can be used to calibrate analysis programs.The phantom can also be used in quality assurance between severallaboratories by comparing clinical protocols, analysis programs andreports. The organs to be simulated by the phantom are the heart, thekidneys and/or the bladder. Additional organs to be simulated by thephantom can be the spleen, the liver, the ureters and soft tissues. Theradiation is detected and imaged by a gamma camera during the simulationof the distribution of radio active solution to the body.

Before the method is started all radiation from the phantom ispreferably isolated to simulate a situation before the entrance of theradio active solution to the body. The isolating is carried out by alead plate between the phantom and the gamma camera. The method is thenstarted by moving out the lead plate between the phantom and the gammacamera to expose the organ or organs to be studied. First, the upperbody is studied and the rest of the lead plate is moved when the rest ofthe body is studied.

At the start of the above exposure, the radiation between the organ tobe studied and the gamma camera is isolated by e.g. movable steel platesbetween the organ to be studied and the gamma camera. Thefilling/emptying of the organ to be studied is simulated by successivelymoving the steel plates from/to the space between the organ to bestudied and the gamma camera so that the increasing of the radiationsimulates the filling of the organ with radio active solution and thedecreasing of the radiation simulates the emptying of the organ to bestudied from radio active solution. The moving parts can be controlledby using a computerized step motor and the functions and the shapes ofthe kidenys can be automated.

In the method of the invention the following steps during detecting theradiation from the phantom is carried in the preferred embodiment,wherein the kidneys, the heart and the bladder is simulate:

The containers simulating the organs to be studied are filled with aradioactive solution,

the lead layer between the gamma camera and the background container ispulled out to simulate the entrance of the radioactive solution to theheart,

radiation from the container simulating the heart is controlled with amoving attenuator situated between the container and the gamma camera,

the rest of the lead layer is pulled out, which mimics the entrance ofthe radiopharmaceutical to the systemic circulation,

the steel plates are moved manually or automatically following an exacttime schedule from the space between the kidneys and the backgroundsimulating the filling of the kidneys,

after moving out of the steel plates, they are moved back to the space,simulating washout of the kidneys,

after the beginning of the kidney washout, the cartridge with the tubessimulating the ureters is placed in the space between the background andthe gamma camera, and finally the radiation from the containersimulating the bladder is controlled with a moving attenuator to mimicfilling of the bladder.

In the phantom described in this study the repeatability is good becausethe dynamics of the simulated kidneys depends only on mechanicalmovement of the steel plates. For the dame reasons the dynamics is easyto change to simulate all possible clinical situations.

The use of the phantom in tests showed its usefulness in multicentrecomparisons and the phantom has a high interoperator reproducibility.The transportation of the phantom is easy in one large box and thereproduction of the phantom and the filling of the activities takesabout 1-2 h. The whole phantom can be used completely by other usersafter a short training.

In advantageous embodiments, the moving parts can be controlled usingcomputerized step motors. In an automated embodiment, the user onlyselect the desired shapes and functions and presses the start buttom.

The phantom is also useful in the calibration procedure of analysisprograms for dynamic radionuclide renography as well as in muiticentrecomparison.

In the following, the invention is described by means of figures andsome examples of preferred embodiments of the device and method of theinvention. It has to be noted that the intention of the followingdetailed description is only for illustrative purposes and that theinvention is not restricted to the details thereof. The scope of theinvention is presented by the claims.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a schematic side view of the device of the invention duringuse.

FIG. 2 is a schematic top view of the phantom of the invention.

FIG. 3 is a schematic view of a part of an automated embodiment of theinvention.

DETAILED DESCRIPTION

The preferred embodiment of the arrangement of the invention comprisesan apparatus with a phantom simulating organs, a gamma camera to detectradioactive radiation from the phantom and steel plates between thephantom and the gamma camera to simulate filling and emptying of radioactive solution to and from the organs of the phantom. The arrangementof the invention in use is presented in FIG. 1 with reference number 1.The phantom part of the arrangement is presented in FIG. 2 withreference number 10. An example of a mechanism of the steel plates of anautomated embodiment of the device of the invention is presented in FIG.3.

The arrangement of the invention is presented in FIG. 1 for calibrationand/or quality assurance of radionuclide renography with referencenumber 1. The arrangement comprises a phantom with containers simulatingdifferent organs. The containers are preferably fastened on a backgroundcartridge or plate, but in FIG. 1 they are drawn separately ofillustrative reasons.

In FIG. 1, the containers simulating the right respective the leftkidney are presented with reference numbers 2 a respective 2 b and theyare filled with a radioactive liquid. The container simulating the heartis presented with reference number 3 and the container simulating thebladder is presented with reference number 4. The phantom may comprise,in addition to the kidney containers 2 a and 2 b, the heart container 3and the bladder container 4, a background container 5 simulating theshapes of the spleen, the liver and the outlines of the soft tissues forvisual purposes. In that case there can be filling tubes one for theliver and one for the other parts of the background. The kidney, heartand bladder containers are covered by lead covers to hinder thepenetration of radiation through other parts than through holes in thelead covers, which holes have the shapes of the simulated organs. Theshapes of the organs can be seen in FIG. 2.

The phantom of FIG. 1 is presented more in detail in FIG. 2 withreference number 10. In FIG. 2, it can be seen that the kidneycontainers 2 a, 2 b have kidney-shaped holes 2 a′, 2 b′ in the leadcover, the heart container 3 has a heart-shaped hole 3′ in the leadcover and the bladder container 4 has a bladder-shaped hole 4′ in thelead cover for the radiation. The background container 5 have shapes forother organs (not illustrated), such as for the spleen, the liver andsoft tissues. There is a space, in an area of the extent of the middlebody of a human being, with a thickness of 4 mm and the thickness at thespleen and the heart is about 8 mm. There is a volume to be separatelyfilled for the liver, to achieve a difference in the imaging substances.

The apparatus of the figures also comprises a lead plate 6 between thebackground container 5 and the gamma camera 11 (or between the steelplates 7 and gamma camera 11 if no background container exist). Thefunction of the lead plate 6 is to reduce radiation from the containersto the gamma camera 11 at the beginning of the examination.

If wanted, the phantom 10 also comprises a cartridge with a plastic tubefilled with radioactive liquid simulating the ureters (not illustrated)to make the phantom more visual and human-like. Reference number 8 is apart made by means of plates to get a space between the camera and thebackground plate, so that a lead plate 6 and said cartridge could bemoved in and out therein during the examination.

The functioning of the heart is simulated using an attenuator 13 for theheart container 3. The attenuator 13 (a lead disc with holes) rotates inthe horizontal plane to cause a heart curve detectable by the camera.The radiation from the heart container 3 penetrates the attenuator 13 sothat the gamma camera detects the distribution of the radio activesolution through the heart.

There is an attenuator 14 also for the bladder container 4 actingsimilarly to the heart bladder 13. The radiation from the bladdercontainer 4 penetrates the attenuator 14 so that the gamma camera cansee the filling of the bladder. The attenuators can for example moveround an axis 12′, 12″ as is illustrated in FIG. 2.

In the radionuclide renography calibration of the invention, thecontainers of the phantom 10 are filled with a radioactive solution,such as a ^(99m)Tc solution. Examples of volumes and activities areshown in table 1. The activities of the containers and the cateters aremade proportional to the patient dosage and the imaging liquid (theradiopharmaceutical) used by the laboratory. Then the phantom 10 ispositioned on the top of the face up collimator 11′ of the gamma camera11. The lead layer 6 is between the background containers 5 and thegamma camera 11 inside the frame 8 and all the steel plates 7 arebetween the kidney containers 2 a and 2 b and the background container5.

The gamma camera 11 is detecting the radioactive radiation 9 from theradioactive solution in the phantom and imaging the situation atroutinely used time intervals. As the function of the lead plate 6 is toreduce radiation from the containers, which are simulating the organsand filled with the radioactive solution, to the gamma camera at thebeginning of the examination, it simulates the situation before theentrance of the radioactive solution to the body.

At the start of the renography, at a time of about 0-5 s, the lead layer6 between the collimator 11′ and the background container 5 inside theframe 8 is pulled out ca 65 mm caudally to simulate the entrance of theradioactive liquid in the body. In other words, when the imaging starts,the lead plate is slowly moved out from the space between the phantomand the camera. The rotation of the attenuator 13 between the heartcontainer and the gamma camera simulates the circulation of imagingagent through the heart.

The rest of the lead layer 6 is pulled out after 19 s, which mimics theentrance of the radiopharmaceutical to the systemic circulation.

Then the steel plates 7 are moved out, preferably one by one, manuallyor by means of an automated mechanism following an exact time schedulefrom the space between the kidneys 2 and the background 5. The timeschedule is designed in accordance with different patient situationsand/or deseases and according to the biochemical processes of the personto be studied. The moving of the steel plates 7 simulates the filling ofthe kidneys which can be detected by the gamma camera 11 as increasingradiation penetrating the plates as the amount of the steel plates 7decreases between the phantom and the camera 11. The moving of the steelplates 7 can for example take place around an axis 12 as in the manualversion of FIG. 1. In the manual version of the invention, thefunctioning of the phantom requires two persons to take care of themoving out of the steel plates 5; one for each kidney. An automatedversion is presented in FIG. 3. After the ca 30-40, for example 36plates, have been moved out, they are moved back to that original space,simulating washout of the kidneys. The amount of steel plates depends onthe time of the biochemical process and how often they are moved one byone.

In the beginning of the kidney washout, the cartridge with the tubesfilled with radioactive liquid simulating the ureters is placed in thespace between the background 5 and the gamma camera 11 inside the frame8. Finally, there is a moving attenuator 14 between the bladdercontainer 4 and the gamma camera 11 for simulating the filling of thebladder.

In another embodiment of the invention (which is not illustrated), therecan be steel plates to simulate the entrance to and filling of the heartinstead of an attenuator. Also the filling of the bladder can besimulated by means of steel plates.

FIG. 3 shows an example of an embodiment of the invention, wherein themoving of the steel plates 7 is automated. It can be generalized with astep motor 20 moving rails 21 up and down. The part 22 takes a plate,which plate is moved by 23. The mechanism can be programmed to do thesteps in accordance with a certain time schedule.

EXAMPLES

The following examples with tables 1-5 was published in Heikkinen, Jari.External quality assurance of nuclear medicine imaging. KuopioUniversity Publications C. Natural and Environmental Sciences 89.1999.50p.

Time-activity Curves

Sex different time schedules and kidney covers were used to simulatethree clinical cases (table 2). In the first case time-activity curvesof the kidneys were generated to simulate normal ^(99m)Tc MAG3 (phantomI, left kidney) and ^(99m)Tc DTPA (phantom I, right kidney) curves(Stabin et al 1992). The second case simulates obstruction (phantom II,left kidney) and hydronephrosis (phantom II, right kidney) and theeffect of diuretics at 10 min after the beginning of the study. Thecurves of the third case were generated from patient studies to simulatefast (phantom III, left kidney) and slow (phantom III, right kidney)function of the kidneys.

Patient Studies

Five ^(99m)Tc DTPA and five ^(99m)Tc MAG3 patient studies were acquiredwith an Elscint Apex 409ECT gamma camera equipped with an all-purposecollimator. The first 64 images were acquired at 1 s intervals and next192 images at 8 s intervals. The age of the DTPA patients was 66+−19years and the injected activity was 181.3+−7.4 MBq. The MAG3 patientshad an age of 61+−19 years and an injected activity of 114.7+−3.7 MBq.

Count Rates

The phantom was imaged as in the patient studies to estimate countrates. Circular (nine pixels) regions of interest (ROI) were drawn onkidneys, soft tissues (inferior to both kidneys), liver, spleen, heartand bladder. Maximum and minimum (after maximum) count rates werecollected and integral calculated from the time activity curves of five^(99m)Tc MAG3, five ^(99m)Tc DTPA patients and three phantom cases(table 2). Values from the patient and the phantom studies were comparedby calculating correlations using a bivariate Pearson two-tailed method.

Precision and Accuracy

A Siemens Orbiter gamma camera equipped with an all-purpose collimatorwas used to define the precision. First 30 images were acquired at 2 sintervals and then 90 images at 20 s intervals. Data nalysis was madewith the renography program of Hermes (nuclear Diagnostics AB,Hägersten, Sweden). Phantom simulations I and II (table 2) were repeatedthree times. The coefficient of variation (CV) of the repeatedmeasurments wqs calculated to express the precision error (Glüer et al1995). The parameters T_(max), T_(½) and 20 min/max (activity at 20 mindivided by the maximum activity) were estimated from the schedules andcompared with the measured values obtained from phantom simulations.Accuracy was defined as a percentage difference between theoretical andmeasured values.

Multicentre Comparison

The simulation with the phantom was made in 19 Finnish nuclear medicinelaboratories that participated in a national multicentre qualityassurance survey in summer 1997. The test was organized by LabqualityLtd. All the laboratories were visited by the inventor and thecontainers filled with activities which produced count rates close toclinical situations; all three patientcases (table 2) were simulated inevery laboratory. One person from each laboratory had to be taught tomove the steel plates of the right kidney.

Results

The count rates produced by the clinical patient studies and the phantomsimulations are seen in table 3. The heart, the kidneys and the bladderproduced very similar count rates in the ^(99m)Tc MAG3 patients and thephantom simulations. Time-activity integrals of the liver, the spleenand the background were also equal. With ^(99m)Tc DTPA patients themaximum count rates are lower and the minimum count rates higher fromthose of the ^(m99)Tc MAG3 patients and the phantom simulations.Although, the activity injected was higher in ^(99m)Tc DTPA than in^(99m)Tc MAG3 patients, the time activity integral of the spleen and thebackground was higher with ^(99m)Tc DTPA than with ^(99m)Tc MAG3.

Precision errors are shown in table 4. The size of the regions ofinterest over the kidneys (area) in the analysis of repeatedmeasurements were not exactly the same. The biggest variation was withthe maximum count rate. Maximum variation of the analysed parameters wasseen in MTT.

The comparison of the three measured parameters and the correspondingvalues estimated from the time schedules are shown in table 5. Thelargest differences are seen in T_(½) with the simulations of the rightkidneys.

Most of the participating laboratories gave an example of their ownpatient study. A visual comparison between patient and simulated phantomprintouts showed a reasonable close approach. In particular a visualcomparison of the produced phantom images and the curves of differentlaboratories seemed very similar. The percentage difference betweenmeasured and theoretical T_(max) values was 6.8+−6.2%, for thesimulation I left kidney 6.9+−5.2% and right kidney 6.7+−7.5% and forthe simulation III 8.5+−7.6% and 5.0+−3.6% respectively. Renography setsof the phantom and the patient studies was performed with variable gammacamera systems (not illustrated).

Discussion

The materials used in the construction of the phantom were chosen fortheir availability price and physical properties. The containers weremade or purchased from plastic and the attenuating material used wassteel. Initial measurements showed that those materials were suitablewhen using different activities of technetium, which produce clinicalcount rates. The use of lead covers over the kidney containers was foundto be practical. One reason for this is radiation safety for the user ofthe phantom and another is that the holes are easy to cut in the lead toproduce kidneys of different shapes.

Embodiment of Invention

The examples were performed with a prototype of the invention, in whichthe function of hte kidneys were simulated by manually movable steelplates. The heart function was simulated non-inventively by filling andemptying a syringe and the bladder function was simulated by moving abladder container cranially.

TABLE 1 Volumes and activities of the containers of the phantomsimulating III MBq patient dose. Volume Activity (ml) (MBq) Kidney 18055.5† Liver 64 2.22 Background 420 7.40 Heart 30 4.63 Ureters 3 0.74†The activity in the left kidney of phantom simulation II was 74 MBq.

TABLE 2 Time schedule for the three phantom simulations. Phantom I:Phantom I: Phantom II: Phantom II: Phantom III: Phantom III: left kidneyright kidney left kidney right kidney left kidney right kidney Plate(s)time Plate(s) time Plate(s) time Plate(s) time Plate(s) time Plate(s)time (number) (min:s) (number) (min:s) (number) (min:s) (number) (min:s)(number) (min:s) (number) (min:s) 1-7 00.40 1-10 00:40 1-8 00:45 1-800:45 1-8 00:40 lead plate 00:50 8-14 00:50 11-21 00:50 9-16 01:00 9-1601:00 9-16 00:50 1-15 01:00 15-28 01:00 22-31 01:00 17-21 01:20 17-2101:20 17-24 01:00 16-22 01:15 29-31 01:40 32 01:10 22-24 01:40 22-2401:40 25-27 01:15 23-24 01:30 32 02:00 33 01:20 25-27 02:00 25-27 02:0028-30 01:30 25 02:00 33 02:20 34 01:40 28 02:20 28 02:15 31-32 01:45 2602:30 34 02:40 35 02:05 29 02:40 29 02:30 33 02:00 27 03:00 35 03:20 3602:30 30 03:00 30 02:45 34 02:20 28 03:15 36 04:00 31 03:30 31 03:00 3502:40 29 03:30 1 03:10 32 04:00 32 03:20 36 03:00 30 03:50 1 05:00 203:50 33 05:00 33 03:40 31 04:00 2 06:00 3 04:30 34 07:00 34 04:20 103:20 32 04.20 3 07:20 4 05:50 35 10:00 35 05:30 2 03:40 33 05:10 408:20 5 07:10 36 14:00 36 07:00 3 04:00 34 06:00 5 09:20 6 09:00Obstruction Hydronephrosis 4 04:20 35 06:30 6 10:00 7 12:00 1 10:30 504:40 36 06:40 7 11:00 8 15:00 2 10:50 6 05:00 8 12:00 9 18:00 3 11:00 705:20 1 06:50 9 12:30 10 21:00 4 11:20 8 05:40 2 07:50 10 13:10 11 26:005 11:50 9 06:00 3 08:50 11 14:00 12 30:00 6 12:10 10 06:30 4 09:20 1214:50 7 12:40 11 07:00 5 10:00 13 15:40 8 13:10 12 07:30 6 10:40 1417:30 9 13:50 13 08:00 7 12:00 15 20:00 10 14:30 14 09:00 8 13:00 1624:00 11 15:10 15 10:00 9 13:40 17 30:00 12 16:40 16 11:00 10 15:00 1318:10 17 12:30 11 17:30 14 19:00 18 14:00 12 20:00 15 19:50 19 16:00 1325:00 16 22:10 20 18:00 14 30:00 17 26:00 21 20:00 18 30:00 22 24:00 2328:00 Lead plate = additional lead plate was placed between the kidneycontainer and gamma camera to simulate low perfusion.

TABLE 3 Count rates from five ^(99m)Tc MAG3, five ^(99m)Tc DTPA andthree phantom studies. Five DTPA Five MAG3 Three phantom patientspatients simulations Average Average Average (cps) SD (cps) SD (cps) SDHeart max 181.8 71.9 118.6 29.6 155.0 15.5 min 23.8 7.7 8.8 4.9 11.7 6.4integral 58619 16884 32913 11021 30519 21254 Left kidney max 87.6 29.7138.2 48.4 162.3 4.0 min 39.4 20.1 31.0 12.2 41.0 8.5 integral 8469633411 108594 31247 141764 64079 Right kidney max 117.0 37.3 154.2 87.5147.0 77.5 min 61.0 41.8 21.4 17.5 50.3 22.3 integral 118386 56804128038 96755 134377 71217 Liver max 59.8 27.2 64.6 17.2 28.0 2.6 min15.6 5.5 14.6 4.5 21.7 7.4 integral 37087 12326 42012 7224 37253 4523Spleen max 62.8 22.0 41.4 5.5 20.7 8.1 min 16.2 4.5 7.8 2.6 17.0 11.3integral 38663 9307 24606 3595 26418 10704 Background max 19.4 5.6 14.62.1 12.3 5.8 min 10.2 3.6 4.8 2.4 9.3 8.4 integral 22046 6503 13908 313016000 8310 Bladder max 139.2 52.9 252.8 75.4 271.5 17.7 min 10.6 23.70.0 0.0 4.0 5.7 integral 132843 41836 269456 94789 194357 9786 cps =counts per second

TABLE 4 The results of the three repeated phantom simulations I and III.Average SD CV (%) PI, left PI, right PIII, left PIII, right PI, left PI,right PIII, left PIII, right Area (cm²) 1.9 41.8 39.8 52.7 36.3 1.3 0.40.7 0.8 Max count rate (cps) 16.5 1139.0 968.0 1443.7 842.0 202.4 138.1226.6 140.1 Perfusion integral (%) 5.5 47.7 52.3 84.0 16.0 3.8 3.8 1.01.0 T_(max) (min) 2.1 4.3 2.7 3.0 6.8 0.0 0.0 0.0 0.2 MTT (min) 10.8 6.35.8 5.0 7.9 0.7 0.5 1.0 0.3 Function Patlak (%) 2.3 51.7 48.3 76.3 23.71.5 1.5 0.6 0.6 Outflow index (%) 1.2 86.0 80.3 91.0 69.7 1.0 1.2 1.00.6 T_(1/2) (min) 5.0 9.1 17.7 3.8 9.0 0.3 0.9 0.2 0.3 20 min/max 4.30.35 0.51 0.22 0.43 0.01 0.01 0.01 0.03 CV = coefficient variation, SD =standard deviation. PI and PIII are phantom simulations I and III. Area= region of interest of the kidney, Outflow index = percentage ofinjected tracer which has been excreted at 20 min. T_(max) = time toreach maximum activity, cps = counts per second, MTT = mean transittime, T_(1/2) = time from maximal to half activity. Perfusion integraland Function Patlak are parameters defined by Hermes (NuclearDiagnostics AB. Hägersten, Sweden). 20 min/max = activity at 20 mindivided by the maximum activity.

TABLE 5 The comparison of the measured parameters and the valuesestimated from the time schedules. Difference Difference DifferenceDifference PI, left Ref. (%) PI, right Ref. (%) PIII, left Ref. (%)PIII, right Ref. (%) T_(max) (min) 4.3 4.5 4.7  2.7 2.8 3.7 3.0 3.2 6.76.8 6.6 −2.9 (4.4 ± 0.4) (2.8 ± 0.3) (3.0 ± 0.3) (7.0 ± 0.4) T_(1/2)(min) 9.1 9.9 8.8 17.7 25.2 42.6 3.8 4.1 7.9 9.0 12.0 3.33 20 min/max0.35 0.36 2.9  0.51 0.55 7.8 0.22 0.24 9.1 0.43 0.47 9.3 PI and PIII arephantom simulations I and III. Figures in parentheses are the T_(max)results of the multicentre comparison between 19 laboratories (average ±SD). T_(max) = time to reach maximum activity, T_(1/2) = time frommaximal to half activity. 20 min/max = activity at time 20 min divide bythe maximum activity. Ref. = value defined from the time schedule.

I claim:
 1. An apparatus for calibration and/or quality assurance ofnuclear medicine imaging, in which functional information of the organsto be studied is achieved by inserting radioactive solution emittingdetectable radiation and by detecting the radiation by a gamma camera,comprising a phantom functionally simulating the organs to be studied,characterized in that the that the organs to be simulated by the phantomare in form of containers filled with radioactive solution, theapparatus further comprising movable isolating parts between thecontainers and the gamma camera to isolate radiation from the containersto the camera.
 2. The apparatus according to claim 1 wherein the organsto be simulated by the phantom is the heart, the kidneys and/or thebladder.
 3. The apparatus according to claim 1 wherein the containerssimulating the organs to be studied are covered by lead and havingorgan-shaped holes for the radiation to be emitted.
 4. The apparatusaccording to claim 1 wherein the movable parts for isolating theradiation are steel plates.
 5. The apparatus according to claim 1wherein it comprises a background container simulating the shapes of thespleen, the liver and the outlines of the soft tissues for visualpurposes.
 6. The apparatus according to claim 5 wherein there is amovable lead plate between the background container and the gamma camerafor regulation and isolation of the radiation from the phantom.
 7. Theapparatus according to claim 1 wherein there is a cartridge comprising aplastic tube filled with radioactive liquid simulating the ureters. 8.The apparatus according to claim 4 wherein the steel plates are movingin accordance with a preset time schedule forth and back to the spacebetween the kidneys and the background for sumulating the filling andwashout of the kidneys.
 9. The apparatus according to claim 2 whereinthe phantom comprises an attenuator circulating at a preset rate tosimulate the central circulation of the radioactive solution through theheart.
 10. The apparatus according to claim 2 wherein the phantomcomprises an attenuator circulating at a preset rate to mimic filling ofthe bladder.
 11. The apparatus according to claim 2 wherein simulate thecentral circulation of the radioactive solution through the heart bymeans of steel plates moving in accordance with a preset time schedule.12. The apparatus according to claim 2 wherein filling of the bladder issimulated by means of steel plates moving in accordance with a presettime schedule.
 13. The apparatus according to claim 2 wherein the movingparts are controlled by using computerized step motors.
 14. Theapparatus according to claim 2 wherein the functions and the shape ofthe kidneys is automated.